Voriconazole and multidrug resistance in Candida albicans.

In vitro activity of voriconazole against fluconazole-resistant Candida albicans clinical isolates with identified molecular basis of multidrug resistance (MDR) and recombinant Saccharomyces cerevisiae expressing C. albicans genes coding for major multidrug transporters, CaCdr1p, CaCdr2p or CaMdr1p, was compared with that of fluconazole, ketoconazole and clotrimazole. It was found that overexpression of the MDR genes made the yeast cells less susceptible to voriconazole. The voriconazole resistance indexes, defined as a ratio of minimum inhibitory concentrations (MICs) determined for MDR and sensitive cells, were comparable with those determined for fluconazole. Voriconazole effectively competed with rhodamine 6G for the active efflux mediated by CaCdr1p and CaCdr2p.